We evaluated the accuracy of PET/CT with 68Ga-PSMA-HBED-CC-a 68Ga-conjugated ligand of human prostate-specific membrane antigen (PSMA)-to localize cancer in the prostate and surrounding tissue at initial diagnosis.
Methods: Twenty-one patients with biopsy-proven prostate cancer underwent 68Ga-PSMA-HBED-CC (68Ga-PSMA) PET/CT at a median of 4 d (range, 0-47 d) before radical prostatectomy. Based on a 6-segment model, the Gleason score and proportion of tumor tissue within each segment (segmental tumor burden, or STB) as determined by histopathology (STBHP) were correlated with SUVmax and STB as determined by different SUV cutoffs for 68Ga-PSMA PET (STBPET1-6). Furthermore, the involvement of seminal vesicles and other extracapsular extension were assessed by histopathology and PET/CT.
Results: Histopathology-positive segments (n = 100 of 126; 79%) demonstrated a significantly higher mean ± SD SUVmax (11.8 ± 7.6) than histopathology-negative segments (4.9 ± 2.9; P < 0.001). Receiver-operating-characteristic analysis revealed an optimal SUVmax cutoff of 6.5 for discrimination of histopathology-positive segments from histopathology-negative segments (area under the curve, 0.84; P < 0.001), which gave 67% sensitivity, 92% specificity, a 97% positive predictive value, a 42% negative predictive value, and 72% accuracy. STBPET3 as determined by (2 × blood SUV) + (2 × SD) correlated best with STBHP (Pearson ρ = 0.68; P < 0.001; mean difference ± SD, 19% ± 15%). PET/CT correctly detected invasion of seminal vesicles (n = 11 of 21 patients; 52%) with 86% accuracy and tumor spread through the capsule (n = 12; 57%) with 71% accuracy.
Conclusion: 68Ga-PSMA PET/CT accurately detected the location and extent of primary prostate cancer. Our preliminary findings warrant further investigation of 68Ga-PSMA PET/CT in conjunction with needle biopsy.
Keywords: PET; PSMA; biopsy; prostate cancer.
© 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.